DESCRIPTION OF THE RELATED ART
As disclosed in Japanese Unexamined Patent Publication Sho 62 (1987)-57957, it is well known that, in a conventional system, when roving bobbins from which rovings are fed to draft parts of a ring spinning frame become almost exhausted and small in size and the yarn packages of the spinning frame reach a predetermined size after the completion of forming a starting portion thereof, i.e., one-third of a full package size thereof, supplemental rovings are taken from the full packaged roving bobbins. These bobbins are prepared in advance in a creel part of a ring spinning frame, during a predetermined period between a time at which the size of the yarn packages reaches one-third of the full yarn package size and a time at which the size of the yarn package becomes 90% of the full yarn package size, and these rovings are carried to positions right above trumpets of the corresponding draft parts of the ring spinning frame, respectively. Thereafter, the above-mentioned supplemental rovings are combined with corresponding rovings fed from the almost exhausted roving bobbins, respectively, and the rovings, which are connected to the respective roving bobbins, are separated from the combined portion of the rovings immediately after the above-mentioned combination. The above-mentioned unit operation is carried out from one end of the spindle alignment of the ring spinning frame to the other end, by utilizing a roving piecing apparatus having a function of synchronously carrying out the unit operation for a group of a plurality of successive spindles, for example, two to six spindles. It is also possible to carrying out the above-mentioned unit operation manually.
In the above mentioned roving piecing operation utilizing the apparatus disclosed in the above-mentioned prior art, the unit operation by the apparatus is carried out by successive operations such as a first operation for reserving supplemental rovings at the respective positions close to the trumpets of the corresponding draft parts, and a second operation, i.e., the joint piecing operation of supplemental rovings with the corresponding rovings, which are fed from the respective roving bobbins, at the above-mentioned positions, and a third operation of cutting the rovings which are supplied from the respective roving bobbins arranged at the creel portion of the ring spinning frame, at the respective positions upstream of the corresponding trumpets of the draft parts, and the above-mentioned unit operation by the apparatus is successively carried out by displacing the apparatus along the spindle alignment. Therefore, the time required to carry out the roving piecing operation at the time of exchanging almost exhausted roving bobbins for the full packages roving bobbins, utilizing the above-mentioned known apparatus is fairly long. This problem becomes more serious when producing a coarse count yarn, which is preferably produced by utilizing a ring spinning frame having a larger number of spindles than the standard size spinning frame, because the time required to produce the full size yarn package is shorter than the time required to complete the successive roving piecing operation for all spindles of the ring spinning frame. Accordingly, the above-mentioned roving piecing method and apparatus are not suitable for producing a coarse count yarn.